1. Field of the Invention
This invention relates to a high-damping composite material comprising metals or alloys; its manufacture and use.
2. Description of the Prior Art
In machine design, particularly in the construction of rotary thermal machines, the question of damping capacity of the material's construction, which are highly stressed mechanically and thermally, is a recurring problem. The greater the damping capacity of the material, and of the component manufactured therefrom, the longer the expected life in operation--with the properties and conditions being otherwise the same. In practice, attempts are made to increase the damping of a machine element by constructional measures and also by measures relating to material technology. Numerous attempts are documented in the literature. Special dampers are built into the machine element or the latter is manufactured completely from a damping material. Laminated materials are also used, a poorly damping base material being provided with a non-metallic damping coating. On the material side it is known that certain alloys, such as 12% Cr steel or NIVCO 10 (Westinghouse) have good magnetoelastic damping. These also include other ferromagnetic alloys (for example, A. W. Cochardt, High-damping ferromagnetic alloys, Transactions AIME, Journal of Metals, October 1956, page 1295-1298; U.S. Pat. Nos. 2,829,048, 2,981,620 and 3,486,886). Special damper designs are also known (for example, D. I. G. Jones, A. D. Nashif and M. Stargardter, Vibrating beam dampers for reducing vibrations in gas turbine blades, ASME publication, Paper No. 74-GT-95, presented at Gas Turbine Conference Zurich, Switzerland, Mar. 31 to Apr. 4, 1974; U.S. Pat. No. 3,601,228).
Highly stressed components of thermal machines, in particular gas turbines, demand materials having a high continuous creep strength and fatigue resistance at high temperature. 12% Cr steel has a comparatively low hot strength at 600.degree. C. and the NIVCO 10 alloy (Westinghouse) is prone to fatigue cracks at this temperature due to the precipitation of a brittle phase comprising intermettalic compounds. It is expensive to build special damping elements into machine components and this limits the design options for the machine components which are already restricted by operational considerations. It is necessary here to match elements of this type, which in most cases are provided with a visco-elastic enamal layer to the specific resonant range occurring in the operation of the machine component. Moreover, the combination of a metallic base material, for example a super alloy, with a non-metallic glassy layer, for example, enamel, cannot be regarded as ideal because of the large differences in their chemical and physical properties. Thus, a need exists for machining components simultaneously possessing good mechanical and thermal strength and good damping properties.